The present invention relates to a method of plating an iron-cobalt alloy and more particularly to a method of plating a thin film of an iron-cobalt alloy useful as a material having magnetic properties required for delay element and the like.
Heretofore, 50% Fe-50% Co alloy, 13% Al-87% Fe alloy, pure nickel and the like are metallurgically produced as magnetostriction materials. However, these magnetostriction materials except for the pure nickel have such drawbacks that the workability is poor and it is impossible to manufacture relatively thin sheets, for example, sheets having a thickness of 0.1 mm. Furthermore, the 13% Al-87% Fe alloy has such a drawback that the solderability is poor. On the other hand, the pure nickel has a good workability, but is inferior in the magnetic properties to the Fe-Co alloy, so that it is not necessarily useful as the magnetostriction material.
Moreover, there has been attempted to improve the workability of the Fe-Co alloy aiming at excellent magnetic properties thereof. For instance, there is a method wherein about 2% of vanadium is added to the Fe-Co alloy. By the addition of vanadium the workability can be improved, but the magnetic properties inherent to the Fe-Co alloy are conversely degraded.
Accordingly, it is difficult to produce satisfactory materials capable of using as the magnetostriction material of this type by the metallurgical method. Further, there are not yet developed effective methods for producing said satisfactory magnetostriction material.
While, the method of plating an iron-cobalt alloy is not developed and utilized in general field because the plated film of iron-cobalt alloy itself is not particularly superior in, for example, abrasion resistance, corrosion resistance or appearance such as gloss and the like to the other plated films. At the same time, there is not yet developed an effective plating method with respect to the iron-cobalt alloy plated film.
As the method of plating Fe-Co alloy, for example, there has been practised a method of plating an iron-cobalt alloy in a plating bath composed of cobalt chloride, ferrous chloride and calcium chloride. In this method, however, the bath temperature among the plating conditions is as high as 80.degree.-90.degree. C., so that the evaporation loss of the plating solution becomes large and also iron hydroxide is formed and precipitated during the plating and consequently this plating bath becomes very unstable. If the bath temperature is less than 80.degree. C., the electrodeposition strain is large and the cracks are caused in the plated film, so that it is difficult to produce the thick plating film. From these reasons, this method is not practical.
Furthermore, there is proposed the use of the plating bath composed of cobalt sulfate, ferrous sulfate and sodium acetate in addition to the above described chloride plating bath. However, this sulfate plating bath is also not practical because of the formation of white precipitates.